A machine type communication (MTC) device is a user equipment (UE) that is used by a machine for specific application (e.g., smart utility meters, parking meters, cars, and home appliances are few examples of MTC UEs). Work has been in progress for enabling MTC UEs to operate within a communication network such as the 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) networks. In the 3GPP Technical Specification Release-12, a Work Item on Low Complexity MTC (LC-MTC) UE was completed according to which the complexity (cost) of a MTC UE is reduced by approximately 50%. In the 3GPP Release-13, another Work Item has been agreed upon, according to which the complexity of a MTC UE is further reduced to enhance the coverage and improve power consumption of MTC UEs.
One technique in achieving LC-MTC UEs is to reduce the radio frequency (RF) bandwidth of an LC-MTC UE to 1.4 MHz (operating with 6 PRBs (where a Physical Resource Block (PRB) is a unit of resource allocation in the frequency domain)). An LC-MTC UE is to be operable in any given system bandwidth and is to co-exist with legacy UEs within a communication network (e.g., cellular phones, Personal Digital Assistants (PDAs), laptops, etc.). Furthermore, a LC-MTC UE is to be able to retune the frequency at which the LC-MTC UE operates, in order to operate in different (1.4 MHz) sub-bands within the system bandwidth (e.g., Long Term Evolution (LTE) communication systems) to allow frequency multiplexing among LC-MTC UEs and also legacy UEs.
For LC-MTC UEs operating in a coverage enhancement mode, the coverage is enhanced through repetition of physical channels. The number of repetitions may be relatively high (hundreds of repetitions), which would in turn impact to the spectra efficiency of the communication system.
The physical channels include Physical Uplink Control Channel (PUCCH) and Physical Uplink Shared Control Channel (PUSCH). A PUCCH channel carries uplink control information (UCI). The resource i.e., physical resource block (PRB) of the PUCCH that carries the UCI are determined implicitly. The PUSCH channel carries uplink data information. Transmission of the PUSCH is scheduled by the downlink control information (DCI) provided to the LC-MTC UE by a serving base station (e.g., a serving eNode B).
In a legacy system, the resources used to transmit PUCCH are at the edge of the system bandwidth, which may be used for PUCCH transmission by LC-MTC UEs. Since a LC-MTC can only operate within a sub-band (e.g., 1.4 MHz), it is not possible to transmit both PUCCH and PUSCH at the same time if PUSCH is in another sub-band. Moreover, in a legacy system, if a PUCCH & PUSCH transmissions collide (i.e. scheduled to transmit at the same subframe), the UCI carried by the PUCCH may be transmitted by piggybacking the PUCCH onto the PUSCH transmission. For a LC-MTC UE operating in normal coverage mode (without repetition), the same mechanism of UCI piggybacking onto the PUSCH transmission may be used when PUCCH & PUSCH collision occurs.
However, for a LC-MTC UE operating in a coverage enhanced mode, PUCCH and PUSCH are repeated and therefore, it is more likely to have PUCCH and PUSCH collisions. Moreover, a PUSCH carrying larger payload would experience longer repetitions compared to that in PUCCH. Hence, unlike collisions in a legacy system as described above, due to differences in repetition and starting times of repetitions in PUCCH and PUSCH, parts of the repetitive samples of PUSCH or PUCCH transmissions encounter collisions.